Poland's acting president, Bronislaw Komorowski, was ahead of the late president's identical twin brother, Jaroslaw Kaczynski, in the presidential election Sunday after 95 per cent of the polls reported.

Poland's Prime Minister Donald Tusk, accompanied by his wife, Malgorzata, votes Sunday in Sopot, near Gdansk. (Krzysztof Mystkowski/Associated Press)

An exit poll also released Sunday by the TNS OBOP institute also predicted Komorowski winning 53.1 per cent of the vote, with Kaczynski taking 46.9 per cent. A separate poll, by Millward Brown SMG/KRC, suggested Komorowski would win 51.1 per cent and Kaczynski 48.9 per cent.

Kaczynski essentially conceded defeat in the presidential run-off by declaring before supporters, "I congratulate the winner."

Officials results based on 95 per cent of polling stations reporting showed that Komorowski won 52.63 per cent of the vote and Kaczynski with 47.37 per cent, the state electoral commission said early Monday.

Full results were expected later on Monday.

Komorowski, the country's acting president and parliamentary speaker, addressed a jubilant crowd in Warsaw. He didn't formally claim victory, noting the votes were still being counted, but expressed optimism he will be the next president.

"Tonight we open a small bottle of champagne and tomorrow we will open a big bottle," he said.

He pledged that as president he would serve all Poles and recalled that the voting was forced by national tragedy — the death of President Lech Kaczynski in a plane crash in April in Smolensk, Russia, along with 95 other Poles.

'In the shadow of catastrophe'

"We thank everybody — the more so that it was an unusual campaign, a difficult campaign held in the shadow of catastrophe," Komorowski, 58, said.

Kaczynski, surrounded by supporters chanting "Jaroslaw!" essentially conceded defeat. "I congratulate the winner. I congratulate Bronislaw Komorowski," Kaczynski said.

Poland's acting President Bronislaw Komorowski, speaker of the parliament and presidential candidate from the Civic Platform Party, waves to supporters next to his wife Anna at his election headquarters in Warsaw on Sunday. (Kacper Pempel/Reuters)

An election was originally set for the fall but had to be called early after Lech Kaczynski's death April 10. It was the worst tragedy to strike Poland in decades and set a tone for a sombre election campaign free of dirty political manoeuvring.

Both candidates in the runoff vote were former anti-communist activists with conservative Roman Catholic upbringings, but they split on key issues, primarily the role of the state in the economy.

Komorowski would be expected to smooth the way for the government to continue privatizing state-run companies and trim welfare benefits, if the exit poll results are accurate.